L

Larynx: the voice box.

Laryngeal: pertaining to the voice box.

Laryngectomy: Surgical removal of the voice box (larynx), usually because of cancer.

Lesion: Change in body tissue; sometimes used as another word for tumor.

Leukemia: Cancer of the blood or blood-forming organs. People with leukemia often have a noticeable increase in white blood cells (leukocytes). Two basic types of leukemia are Hodgkins Disease and Non-Hodgkins Disease. Of the two, Non-Hodgkins is generally more difficult to treat.

Leukocytosis: Possessing more than the usual number of white blood cells.

Leukopenia: Decrease in the white blood cell count, often a side effect of chemotherapy.

Leukoplakia: Formation of white patches on tongue or cheek - often pre-malignant.

LHRH (leuteinizing hormone-releasing hormone): Hormone produced by the hypothalamus, a gland in the brain.

LHRH analogs: Man-made hormones that are chemically similar to LHRH. They block production of the male hormone testosterone and sometimes are used to treat prostate cancer.

Library (in biotech terminology): An unordered collection of clones (i.e., cloned DNA from a particular organism), whose relationship to each other can be established by physical mapping. Compare genomic library, arrayed library.

Limited breast surgery: Called lumpectomy, this is a segmental excision, and tylectomy. The surgery removes the breast cancer and a small amount of tissue around the cancer, but preserves most of the breast. It is almost always combined with lymph node removal and is usually followed by radiation.

Linear accelerator: Machine that gives off gamma rays and electron beams to treat cancer.

Linkage: The proximity of two or more markers (e.g., genes, RFLP markers) on a chromosome; the closer together the markers are, the lower the probability that they will be separated during DNA repair or replication processes (binary fission in prokaryotes, mitosis or meiosis in eukaryotes), and hence the greater the probability that they will be inherited together.

Linkage map: A map of the relative positions of genetic loci on a chromosome, determined on the basis of how often the loci are inherited together. Distance is measured in centimorgans (cM).

Lobectomy: Surgical removal of a lobe of an organ--usually the lung.

Lobular carcinoma in situ (LCIS): Very early stage breast cancer that develops within the milk-producing glands (lobules) and does not penetrate through the walls of the lobules. Researchers think most cases of lobular carcinoma in situ do not progress to invasive lobular cancer. However, having this type of cancer places a woman at increased risk of developing invasive breast cancer later in life. It is important for women with lobular carcinoma in situ to have a physical examination three times a year and an annual mammogram.

Lobules: Glands in a woman's breasts that produce milk.

Localize: Determination of the original position (locus) of a gene or other marker on a chromosome.

Localized cancer: One confined to the place where it started and not spread to distant parts of the body.

Locus (pl. loci): The position on a chromosome of a gene or other chromosome marker; also, the DNA at that position. The use of locus is sometimes restricted to mean regions of DNA that are expressed. See gene expression.

Lump: Any tissue mass in the breast or elsewhere in the body.

Lumpectomy: Surgical removal of a breast tumor and a small amount of surrounding normal tissue. (See: Breast conservation therapy, Two-step procedure.)

Lymph limf: Clear fluid that flows through lymphatic vessels and contains cells known as lymphocytes. Lymphocytes are important in fighting infections and may also have a role in fighting cancer.

Lymph nodes: Bean-shaped collections of immune system tissue such as lymphocytes, found along lymphatic vessels that remove cell waste and fluids from lymph. They help fight infections and also have a role in fighting cancer. Also called lymph glands.

Lymphatic system: Tissues and organs (including lymph nodes, spleen, thymus, and bone marrow) that produce and store lymphocytes (cells that fight infection) and the channels that carry lymph fluid. The entire system is an important part of the body's immune system. Invasive cancers sometimes penetrate the lymphatic vessels (channels) and spread (metastasize) to lymph nodes.

Lymphedema: Complication that may happen after breast cancer treatment. Swelling in the arm is caused by excess lymph fluid that collects after lymph nodes and vessels are removed by surgery or treated by radiation. This condition can be persistent but not painful. (Also may simply be referred to "Edema".)
 
Lymphocytes: Specialized white blood cell that helps the body fight infection.

Lymphocytosis: Having excess lymphocytes.

Lymphokines: (See: Cytokine.)

Lymphoma: Lymphatic system cancer. The lymphatic system is a network of thin vessels and nodes throughout the body designed to fight infection. Lymphoma involves a type of white blood cells called lymphocytes. The two main types of lymphoma are Hodgkin's disease and non-Hodgkin's lymphoma. The treatment methods for these two types of lymphomas are very different.

Long-Range Restriction Mapping: Restriction enzymes are proteins that cut DNA at precise locations.

Restriction maps depict the positions on chromosomes of restriction enzyme cutting sites. These are used as biochemical "signposts", or markers of specific areas along the chromosomes. The map will detail the positions on the DNA molecule that are cut by particular restriction enzymes.